During operation, turbine engines exhaust a complex mixture of air pollutants. These air pollutants may include oxides of nitrogen (NOx). Exhaust emission standards regulate the amount of NOx emitted to the atmosphere from a turbine engine depending on the type, size, and/or class of the engine. It is known that a well-distributed flame having a low flame temperature may help to reduce NOx emission to levels compliant with emission regulations. One way to generate a flame with a low temperature is to premix fuel and air to a create a lean fuel-air mixture. However, naturally occurring combustion induced pressure fluctuations within the combustor of the turbine engine can be amplified during operation of the engine under lean conditions. These amplified pressure fluctuations may induce mechanical vibrations that can damage the turbine engine.
One method to provide a lean fuel-air mixture to a turbine engine while minimizing the harmful vibrations is described in U.S. Patent Publication No. US 2007/0074518 A1 (“the '518 publication”) assigned to the assignee of the current application. In the '518 publication, the length of different regions of a fuel nozzle is adjusted such that a magnitude of the fuel to air equivalence ratio reaching the flame front is a minimum when a pressure pulse at the flame front is a maximum. While the method described in the '518 publication is suitable to reduce mechanical vibrations in many applications, other applications may benefit from other means of reducing mechanical vibrations.
The disclosed fuel injector is directed to overcoming one or more of the problems set forth above.